diff --git a/crates/egui/src/containers/popup.rs b/crates/egui/src/containers/popup.rs
index 8cd545dd0..beee9f900 100644
--- a/crates/egui/src/containers/popup.rs
+++ b/crates/egui/src/containers/popup.rs
@@ -179,6 +179,7 @@ pub struct Popup<'a> {
 
     /// Default width passed to the Area
     width: Option<f32>,
+    sizing_pass: bool,
     sense: Sense,
     interactable: bool,
     layout: Layout,
@@ -202,6 +203,7 @@ impl<'a> Popup<'a> {
             alternative_aligns: None,
             gap: 0.0,
             width: None,
+            sizing_pass: false,
             sense: Sense::click(),
             interactable: true,
             layout: Layout::default(),
@@ -401,6 +403,19 @@ impl<'a> Popup<'a> {
         self
     }
 
+    /// Force the popup's underlying [`Area`] to run an invisible sizing pass.
+    ///
+    /// Popups automatically run a sizing pass when they open or reopen. Set this to `true` for
+    /// one frame when the contents of an already open popup change and its cached size may no
+    /// longer fit. Do not leave it enabled continuously, because the popup would remain invisible.
+    ///
+    /// Default: `false`.
+    #[inline]
+    pub fn sizing_pass(mut self, sizing_pass: bool) -> Self {
+        self.sizing_pass = sizing_pass;
+        self
+    }
+
     /// Set the id of the Area.
     #[inline]
     pub fn id(mut self, id: Id) -> Self {
@@ -556,6 +571,7 @@ impl<'a> Popup<'a> {
             alternative_aligns: _,
             gap,
             width,
+            sizing_pass,
             sense,
             interactable,
             layout,
@@ -584,7 +600,7 @@ impl<'a> Popup<'a> {
             .sense(sense)
             .interactable(interactable)
             .layout(layout)
-            .sizing_pass(!was_open_last_frame)
+            .sizing_pass(sizing_pass || !was_open_last_frame)
             .info(info.unwrap_or_else(|| {
                 UiStackInfo::new(kind.into()).with_tag_value(
                     MenuConfig::MENU_CONFIG_TAG,
diff --git a/crates/egui_kittest/tests/popup.rs b/crates/egui_kittest/tests/popup.rs
index 4dbe33909..9d9dba654 100644
--- a/crates/egui_kittest/tests/popup.rs
+++ b/crates/egui_kittest/tests/popup.rs
@@ -67,6 +67,85 @@ fn reopened_popup_resizes_for_wider_items() {
     );
 }
 
+#[test]
+fn open_popup_resizes_after_explicit_sizing_pass() {
+    const POPUP_BUTTON: &str = "Growing popup";
+    const MAX_HEIGHT: f32 = 100.0;
+
+    struct State {
+        item_count: usize,
+        needs_sizing_pass: bool,
+        popup_height: f32,
+        viewport_height: f32,
+        content_height: f32,
+    }
+
+    let mut harness = Harness::builder()
+        .with_size(egui::Vec2::new(500.0, 300.0))
+        .build_ui_state(
+            |ui, state| {
+                let response = ui.button(POPUP_BUTTON);
+                let needs_sizing_pass = core::mem::take(&mut state.needs_sizing_pass);
+                let item_count = state.item_count;
+
+                if let Some(popup) = Popup::from_response(&response)
+                    .sizing_pass(needs_sizing_pass)
+                    .show(|ui| {
+                        egui::ScrollArea::vertical()
+                            .max_height(MAX_HEIGHT)
+                            .show(ui, |ui| {
+                                for index in 0..item_count {
+                                    ui.label(format!("Item {index}"));
+                                }
+                            })
+                    })
+                {
+                    state.popup_height = popup.response.rect.height();
+                    state.viewport_height = popup.inner.inner_rect.height();
+                    state.content_height = popup.inner.content_size.y;
+                }
+            },
+            State {
+                item_count: 2,
+                needs_sizing_pass: false,
+                popup_height: 0.0,
+                viewport_height: 0.0,
+                content_height: 0.0,
+            },
+        );
+
+    harness.run();
+    let initial_popup_height = harness.state().popup_height;
+
+    harness.state_mut().item_count = 20;
+    harness.run();
+    let stale_viewport_height = harness.state().viewport_height;
+    assert!(
+        stale_viewport_height < MAX_HEIGHT,
+        "viewport unexpectedly reached its maximum without a sizing pass"
+    );
+
+    harness.state_mut().needs_sizing_pass = true;
+    harness.run();
+
+    assert!(
+        harness.state().popup_height > initial_popup_height,
+        "popup did not grow after an explicit sizing pass"
+    );
+    assert!(
+        harness.state().viewport_height > stale_viewport_height,
+        "scroll viewport did not grow after an explicit sizing pass"
+    );
+    assert!(
+        (harness.state().viewport_height - MAX_HEIGHT).abs() <= 0.5,
+        "scroll viewport did not stop at its maximum height"
+    );
+    assert!(
+        harness.state().content_height > harness.state().viewport_height,
+        "popup contents did not remain scrollable at the maximum height"
+    );
+}
+
 #[test]
 fn test_interactive_tooltip() {
     struct State {